1. Field of the Invention
The present invention relates to a lens driving device for driving an image stabilizing lens, an image stabilizing unit including the lens driving device, and an image pickup apparatus including the image stabilizing unit.
2. Description of the Related Art
In recent years, with the advent of cameras with increased functionality, many cameras have included an image stabilizing unit that reduces image blur caused by vibration of the cameras. For example, Japanese Patent Laid-Open No. 60-143330 describes an image stabilizing unit that detects vibration, such as a camera shake, on the basis of a gyro signal so as to stabilize an image by moving a part of an optical system in a direction perpendicular to the light axis. This method has been widely used.
It is desirable that a mechanism of image stabilization provides the following two features: (a) small friction that allows excellent trackability to be provided and (b) easy design of a frequency characteristic for designers. A variety of mechanisms have already provided these features.
For example, Japanese Patent Laid-Open No. 8-184870 describes a mechanism including a lens driving device and a resilient unit and a viscous unit that restrict the displacement of a movable part. Such a structure can provide a mechanism that enables control known as “open control” and an improvement of a frequency characteristic.
In addition, Japanese Patent Laid-Open No. 2001-290184 describes a mechanism that includes a plurality of balls sandwiched by a support member that supports a compensation lens and a stationary member, and the support member is urged by a resilient member. Such a structure can drive the support member using rolling friction, and therefore, can reduce a frictional force. Additionally, since a resonance frequency is determined by a ratio of the weight of the compensation lens and the support member to the elastic coefficient of the resilient member, a desired resonance frequency can be easily obtained. As a result, excellent controllability can be obtained so that the mechanism can appropriately respond to even a small vibration.
In addition, Japanese Patent Laid-Open No. 2-232824 describes a mechanism in which a damping unit is attached to an actuator used for an optical disc pickup. This mechanism is characterized in that appropriate portions of the mechanism are filled with a gel damping material serving as a damping unit. As a result, the improved frequency characteristic of an apparatus can be provided with improved workability.
According to the technology described in Japanese Patent Laid-Open No. 8-184870, a viscous resistance can be obtained using a mechanical or electrical method. However, to obtain a viscous resistance through a mechanical method, the structure is disadvantageously complicated and a frictional force is disadvantageously increased. In contrast, to obtain a viscous resistance through an electrical method, the mechanism disadvantageously has a negative impact from an assembly-to-assembly variation in an object to be controlled. In addition, the control system disadvantageously becomes complicated.
According to the technology described in Japanese Patent Laid-Open No. 2001-290184, a compensation lens can be driven with a very small frictional force and can respond to a small camera shake. However, since this mechanism cannot provide an appropriate viscous resistance, the mechanism is greatly affected by a primary resonance and a sub-resonance, that is, the mechanism is easily affected by disturbance.
According to the technology described in Japanese Patent Laid-Open No. 2-232824, the mechanism can easily obtain an appropriate viscous resistance. However, the structure is not always suitable for image stabilizing units.
Therefore, it would be desirable to provide a lens driving device, an image stabilizing unit, and an image pickup apparatus having a simplified structure in which the location of a support member can be changed relative to a stationary member with an appropriate viscous damping.